Method and system for extending dynamic range of an rf signal

ABSTRACT

Aspects of a method and system for extending dynamic range of an RF signal are provided. In this regard, a signal representative of an amplitude of a pair of baseband signals may be generated. The amplitude of the generated signal may be expanded, and the amplitude of the baseband signals may be compressed. In this regard, the compression and the expansion may be inverse functions of each other. Additionally, the compressed baseband signals may be combined to generate an intermediate signal which may be amplitude modulated by the expanded signal. The amplitude modulation may result from controlling a gain, a voltage source, and/or a current source of a power amplifier. The intermediate signal may be generated by up-converting the baseband signals and subsequently combining the up-converted signals.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This patent application makes reference to, claims priority to andclaims benefit from U.S. Provisional Patent Application Ser. No.60/953,090 filed on Jul. 31, 2007.

The above stated application is hereby incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to signal processing. Morespecifically, certain embodiments of the invention relate to a methodand system for extending dynamic range of an RF signal.

BACKGROUND OF THE INVENTION

As electronic communications are increasingly relied upon to providefast and reliable delivery of information, significant efforts exist toincrease data rates in a variety of communications system. In thisregard, a problem often encountered by communication system designerswhen attempting to increase data rates, is that supporting very highdata rates often requires the utilization of high-order modulationschemes. However, modulation may require highly linear amplifiers andachieving good linearity in a power amplifier often results in reducedefficiency. Accordingly, it may be difficult to achieve highly linearpower amplifiers in, for example, portable devices where powerefficiency is very important due to limited battery capacity. Therefore,systems designers are often forced to balance a tradeoff between highdata rates and power efficiency.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method is provided for extending the dynamic range of anRF signal, substantially as shown in and/or described in connection withat least one of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 a is a block diagram illustrating extending the dynamic range ofan RF signal, in accordance with an embodiment of the invention.

FIG. 1 b is a block diagram illustrating extending the dynamic range ofan RF signal, in accordance with an embodiment of the invention.

FIG. 2 is a flow chart illustrating exemplary steps for extending thedynamic range of an RF signal, in accordance with an embodiment of theinvention.

FIG. 3 is a block diagram illustrating an exemplary wireless device, inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor extending dynamic range of an RF signal. In this regard, a signalrepresentative of an amplitude of a pair of baseband signals may begenerated; the amplitude of the generated signal may be expanded, andthe amplitude of the baseband signals may be compressed. In this regard,the compression and the expansion may be inverse functions of eachother. Additionally, the compressed baseband signals may be combined togenerate an intermediate signal which may be amplitude modulated by theexpanded signal. The amplitude modulation may result from controlling again, a voltage source, and/or a current source of a power amplifier.The signal representative of the amplitude of the baseband signals maybe generated by squaring each of the baseband signals and calculatingthe square root of a sum of the squared baseband signals. Theintermediate signal may be generated by up-converting the basebandsignals and subsequently combining the up-converted signals. In thisregard, the up-conversion may comprise mixing an in-phase signal of saidcompressed signals with a first local oscillator signal and mixing aquadrature-phase signal of said compressed signals with a second localoscillator signal, wherein said first local oscillator signal and saidsecond local oscillator signal are in phase-quadrature.

FIG. 1 a is a block diagram illustrating an exemplary structure forextending the dynamic range of an RF signal, in accordance with anembodiment of the invention. Referring to FIG. 1 a there is shown aportion of an RF transmitter 100 comprising compression blocks 102 a and102 b, mixers 104 a and 104 b, summer 106, power amplifier (PA) 108, andexpansion block 110.

The compression blocks 102 a and 102 b may comprise suitable logic,circuitry, and/or code that may enable reducing the ratio of peak toaverage voltage, current, and/or power of a signal. In this regard, thecompression block 102 a and 102 b may attenuate higher amplitudeportions of signals while passing portions of a signal near DC. Forexample, the compression blocks 102 a and 102 b may operate in a mannersimilar to an amplifier with linear gain for low signal amplitude andincreasing attenuation at higher signal amplitudes.

The mixers 104 a and 104 b may each comprise suitable logic, circuitry,and/or code that may enable generating inter-modulation productsresulting from the mixing of two signals. In this regard, the mixers 104a and 104 b may enable up-conversion of a baseband signal by mixing thebaseband signal with a local oscillator (LO) signal.

The summer 106 may comprise suitable logic, circuitry, and/or code thatmay enable combining two signals. In this regard, the output of thesummer 108 may be equal to the addition of the two inputs of the summer108.

The power amplifier 108 may comprise suitable logic, circuitry, and/orcode that may enable buffering and/or amplification of an RF signal andoutput of the signal to, for example, an antenna for transmission. Inthis regard, the gain of the PA 108 may be adjustable and may enabletransmitting signals of varying strength. Accordingly, the PA 108 mayreceive one or more control signals. In various embodiments of theinvention, controlling the gain of the PA 108 may enable amplitudemodulation of an RF signal.

The expansion block 110 may comprise suitable logic, circuitry, and/orcode that may enable performing the inverse, or opposite, of thecompression function performed by the compression blocks 102 a and 102b. In this regard, the expansion block 110 may amplify portions of asignal that the compression blocks 102 a and 102 b may attenuate.

In an exemplary operation, the signals I(t) and Q(t) may be compressedprior to being up-converted and summed. In this regard, the ratio ofpeak to average voltage, power, and/or current may be reduced. In thismanner, because of the reduced swing of the signal into the PA 108, thePA 108 may be operated closer to its 1 dB compression point, which mayresult in increased efficiency. However, the signal into the PA 108 haseffectively been distorted, and thus to recover information comprisingthe signal, the distortion may need to be reversed. Accordingly, thegain of the PA 108 may be modulated by the output of the expansion block110. Accordingly, the amplitude modulation via controlling the gain ofthe PA 108, may, in effect, reverse the compression performed by thecompression blocks 102 a and 102 b. Accordingly, the output of the PA108 may be as given below in EQ. 1.

s(t)=A sin(ωct+φ)   EQ. 1

where ‘ω’ is angular frequency, ‘c’ is a constant, ‘t’ is time, and φ isphase of the signals I and Q.

FIG. 1 b is a block diagram illustrating an exemplary structure forextending the dynamic range of an RF signal, in accordance with anembodiment of the invention. Referring to FIG. 1 b there is shown aportion of an RF transmitter 100 comprising compression blocks 102 a and102 b, mixers 104 a and 104 b, summer 106, power amplifier (PA) 108,expansion block 110, and power regulator 112.

Each of he compression blocks 102 a and 102 b, the mixers 104 a and 104b, the summer 106, the power amplifier 108, and the expansion block 110may be as described with respect to FIG. 1 a.

The power regulator 112 may comprise suitable logic, circuitry, and/orcode that may enable controlling a voltage and/or current provided tothe PA 108. For example, the power regulator 112 may comprise aswitching voltage regulator, a voltage controlled current source, or abinary weighted current source. Accordingly, a voltage and/or currentoutput by the power regulator 112 may be determined, at least in part,by a control signal communicatively coupled to the power regulator 112.

In operation, a signal output by the expansion block 110 may modulatethe output voltage and/or current of the power regulator 112.Accordingly, the output of the PA 108 may be modulated by controllingthe power supplied to the PA 108. For example, for a switchingregulator, a duty cycle of the power regulator 112 may be controlled, atleast in part, based on the signal from the expansion block 112.Similarly, for a binary weighted current source, the amount of currentsupplied to the PA 108 may be based on the value of the signal output bythe expansion block 110. In this regard, the output of the expansionblock may comprise ‘n’ bits, each of which may control whether one of‘n’ switches comprising the current source is open or closed. In anotherexample, the power regulator 112 may comprise a voltage dependantcurrent source. Accordingly, the current supplied to the PA 108 may bebased, at least in part, on a voltage output by the expansion block 112.

FIG. 2 is a flow chart illustrating exemplary steps for extending thedynamic range of an RF signal, in accordance with an embodiment of theinvention. Referring to FIG. 2 the exemplary steps may begin with startstep 202. Subsequent to step 202, the exemplary steps may advance tostep 203. In step 203 a signal that is representative of an amplitude ofa pair phase-quadrature baseband signals may be generated. Additionally,the amplitude of the generated signal may be expanded. Subsequent tostep 203, the exemplary steps may advance to step 204. In step 204, theratio of peak to average voltage, current, and/or power of the in-phase(I) and quadrature-phase (Q) baseband signals may be compressed. In thisregard, signal swing of the I and Q signals may be reduced such that apower amplifier (PA) amplifying the signals may operate closer to its1dB compression point without saturating or distorting the signal.

Subsequent to step 204, the exemplary steps may advance to step 206. Instep 206, the compressed I and Q baseband signals may be up-converted toRF. In this regard, the I signal may be mixed with an in-phase localoscillator (LO) signal for up-conversion. Similarly, the Q signal may bemixed with a quadrature-phase LO signal for up-conversion. Subsequent tostep 206, the exemplary steps may advance to step 208. In step 208, theup-converted I and Q signals may be combined. In this regard, thesignals may be added together to generate a single RF signal. Subsequentto step 208, the exemplary steps may advance to step 210.

In step 210, the RF signal may be amplified by a power amplifier. Invarious embodiments of the invention, the output of the PA may bemodulated by the expanded amplitude signal generated in step 203. Inthis regard, the expansion of the signal in step 203 may be an inverseoperation of the compression performed in step 204. The output of the PAmay be modified by modulating a gain, a bias point, a supply voltage, asupply current, and/or other parameter of the PA. Subsequent to step210, the exemplary steps may advance to step 212. In step 212 the outputof the PA may be transmitted by, for example, an antenna such as theantenna 321 b of FIG. 3.

FIG. 3 is a block diagram illustrating an exemplary wireless device, inaccordance with an embodiment of the invention. Referring to FIG. 3,there is shown a wireless device 320 that may comprise an RF receiver323 a, an RF transmitter 323 b, a digital baseband processor 329, aprocessor 325, and a memory 327. A receive antenna 321 a may becommunicatively coupled to the RF receiver 323 a. A transmit antenna 321b may be communicatively coupled to the RF transmitter 323 b. Thewireless device 320 may be operated in a system, such as the cellularnetwork and/or digital video broadcast network, for example.

The RF receiver 323 a may comprise suitable logic, circuitry, and/orcode that may enable processing of received RF signals. The RF receiver323 a may enable receiving RF signals in a plurality of frequency bands.For example, the RF receiver 323 a may enable receiving signals incellular frequency bands. Each frequency band supported by the RFreceiver 323 a may have a corresponding front-end circuit for handlinglow noise amplification and down conversion operations, for example. Inthis regard, the RF receiver 323 a may be referred to as a multi-bandreceiver when it supports more than one frequency band. In anotherembodiment of the invention, the wireless device 320 may comprise morethan one RF receiver 323 a, wherein each of the RF receiver 323 a may bea single-band or a multi-band receiver.

The RF receiver 323 a may down convert the received RF signal to abaseband signal that comprises an in-phase (I) component and aquadrature (Q) component. The RF receiver 323 a may perform direct downconversion of the received RF signal to a baseband signal, for example.In some instances, the RF receiver 323 a may enable analog-to-digitalconversion of the baseband signal components before transferring thecomponents to the digital baseband processor 329. In other instances,the RF receiver 323 a may transfer the baseband signal components inanalog form.

The digital baseband processor 329 may comprise suitable logic,circuitry, and/or code that may enable processing and/or handling ofbaseband signals. In this regard, the digital baseband processor 329 mayprocess or handle signals received from the RF receiver 323 a and/orsignals to be transferred to the RF transmitter 323 b, when the RFtransmitter 323 b is present, for transmission to the network. Thedigital baseband processor 329 may also provide control and/or feedbackinformation to the RF receiver 323 a and to the RF transmitter 323 bbased on information from the processed signals. In this regard, thebaseband processor 327 may provide a control signal to one or more ofthe compression blocks 102 a and 102 b, the expansion block 110, themixers 108 a and 108 b, the summer 106, and/or the Pa 108. The digitalbaseband processor 329 may communicate information and/or data from theprocessed signals to the processor 325 and/or to the memory 327.Moreover, the digital baseband processor 329 may receive informationfrom the processor 325 and/or to the memory 327, which may be processedand transferred to the RF transmitter 323 b for transmission to thenetwork.

The RF transmitter 323 b may comprise suitable logic, circuitry, and/orcode that may enable processing of RF signals for transmission. The RFtransmitter 323 b may enable transmission of RF signals in a pluralityof frequency bands. For example, the RF transmitter 323 b may enabletransmitting signals in cellular frequency bands. Each frequency bandsupported by the RF transmitter 323 b may have a corresponding front-endcircuit for handling amplification and up conversion operations, forexample. In this regard, the RF transmitter 323 b may be referred to asa multi-band transmitter when it supports more than one frequency band.In another embodiment of the invention, the wireless device 320 maycomprise more than one RF transmitter 323 b, wherein each of the RFtransmitter 323 b may be a single-band or a multi-band transmitter.

The RF transmitter 323 b may quadrature up convert the baseband signalcomprising I/Q components to an RF signal. The RF transmitter 323 b mayperform direct up conversion of the baseband signal to a RF signal, forexample. The RF transmitter may be enabled to polar modulate one or morecarrier signals by the baseband signal. In this regard, the RFtransmitter may be enabled to separate the generation of phase andamplitude components of a signal to be transmitted. In this manner, theRF transmitter may be enabled to perform phase modulation independent ofamplitude modulation. In some instances, the RF transmitter 323 b mayenable digital-to-analog conversion of the baseband signal componentsreceived from the digital baseband processor 329 before up conversion.In other instances, the RF transmitter 323 b may receive baseband signalcomponents in analog form.

The processor 325 may comprise suitable logic, circuitry, and/or codethat may enable control and/or data processing operations for thewireless device 320. The processor 325 may be utilized to control atleast a portion of the RF receiver 323 a, the RF transmitter 323 b, thedigital baseband processor 329, and/or the memory 327. In this regard,the processor 325 may generate at least one signal for controllingoperations within the wireless device 320. In this regard, the processor325 may provide a control signal to one or more of the compressionblocks 102 a and 102 b, the expansion block 110, the mixers 108 a and108 b, the summer 106, and/or the Pa 108. The processor 325 may alsoenable executing of applications that may be utilized by the wirelessdevice 320. For example, the processor 325 may execute applications thatmay enable displaying and/or interacting with content received viacellular transmission signals in the wireless device 320.

The memory 327 may comprise suitable logic, circuitry, and/or code thatmay enable storage of data and/or other information utilized by thewireless device 320. For example, the memory 327 may be utilized forstoring processed data generated by the digital baseband processor 329and/or the processor 325. The memory 327 may also be utilized to storeinformation, such as configuration information, that may be utilized tocontrol the operation of at least one block in the wireless device 320.For example, the memory 327 may comprise information necessary toconfigure the RF receiver 323 a to enable receiving cellulartransmission in the appropriate frequency band. In this regard, thememory 327 may store control and/or configuration information for to oneor more of the compression blocks 102 a and 102 b, the expansion block110, the mixers 108 a and 108 b, the summer 106, and/or the Pa 108.

Aspects of a method and system for extending dynamic range of an RFsignal are provided. In this regard, a signal, A(t), representative ofan amplitude of a pair of baseband signals, I(t) and Q(t), may begenerated. The amplitude of the generated signal, A(t), may be expanded,and the amplitude of the baseband signals I(t) and Q(t) may becompressed. In this regard, the compression and the expansion may beinverse functions of each other. Additionally, the compressed basebandsignals may be combined, by the summer 106, to generate an intermediatesignal which may be amplitude modulated by the expanded signal. Theamplitude modulation may result from controlling a gain, a voltagesource, and/or a current source of the power amplifier 108. The signalrepresentative of the amplitude of the baseband signals may be generatedby squaring each of the baseband signals and calculating the square rootof a sum of the squared baseband signals. The intermediate signal may begenerated by up-converting the baseband signals and subsequentlycombining the up-converted signals. In this regard, the up-conversionmay comprise mixing, via the mixer 104 a, an in-phase signal of saidcompressed signals with a first local oscillator signal and mixing, viathe mixer 104 b, a quadrature-phase signal of said compressed signalswith a second local oscillator signal, wherein said first localoscillator signal and said second local oscillator signal are inphase-quadrature

Another embodiment of the invention may provide a machine-readablestorage, having stored thereon, a computer program having at least onecode section executable by a machine, thereby causing the machine toperform the steps as described herein for extending dynamic range of anRF signal.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for signal processing, the method comprising: generating asignal that is representative of an amplitude of a pair of basebandsignals; expanding an amplitude of said generated signal; compressing anamplitude of each signal of said pair of baseband signals; generating anintermediate signal from said compressed signals; and amplitudemodulating said intermediate signal by said expanded signal.
 2. Themethod according to claim 1, comprising squaring each signal of saidpair of baseband signals and calculating a square root of a sum of saidsquared signals to generate said signal that is representative of anamplitude of said pair of baseband signals.
 3. The method according toclaim 1, comprising generating said intermediate signal by up-convertingsaid compressed signals and combining said up-converted signals.
 4. Themethod according to claim 3, comprising up-converting said compressedsignals by mixing an in-phase signal of said compressed signals with afirst local oscillator signal and mixing a quadrature-phase signal ofsaid compressed signals with a second local oscillator signal, whereinsaid first local oscillator signal and said second local oscillatorsignal are in phase-quadrature.
 5. The method according to claim 1,comprising amplitude modulating said intermediate signal by controllinga gain of a power amplifier.
 6. The method according to claim 1,comprising amplitude modulating said intermediate signal by controllinga current source supplying a power amplifier.
 7. The method according toclaim 1, comprising amplitude modulating said intermediate signal bycontrolling a voltage source supplying a power amplifier.
 8. The methodaccording to claim 1, wherein said expansion is an inverse function ofsaid compression.
 9. A machine-readable storage having stored thereon, acomputer program having at least one code section for signal processing,the at least one code section being executable by a machine for causingthe machine to perform steps comprising: generating a signal that isrepresentative of an amplitude of a pair of baseband signals; expandingan amplitude of said generated signal; compressing an amplitude of eachsignal of said pair of baseband signals; generating an intermediatesignal from said compressed signals; and amplitude modulating saidintermediate signal by said expanded signal.
 10. The machine-readablestorage according to claim 9, wherein said at least one code sectioncomprises code for squaring each signal of said pair of baseband signalsand calculating a square root of a sum of said squared signals togenerate said signal that is representative of an amplitude of said pairof baseband signals.
 11. The machine-readable storage according to claim9, wherein said at least one code section comprises code for generatingsaid intermediate signal by up-converting said compressed signals andcombining said up-converted signals.
 12. The machine-readable storageaccording to claim 11, wherein said at least one code section comprisescode for up-converting said compressed signals by mixing an in-phasesignal of said compressed signals with a first local oscillator signaland mixing a quadrature-phase signal of said compressed signals with asecond local oscillator signal, wherein said first local oscillatorsignal and said second local oscillator signal are in phase-quadrature.13. The machine-readable storage according to claim 9, wherein said atleast one code section comprises code for amplitude modulating saidintermediate signal by controlling a gain of a power amplifier.
 14. Themachine-readable storage according to claim 9, wherein said at least onecode section comprises code for amplitude modulating said intermediatesignal by controlling a current source supplying a power amplifier. 15.The machine-readable storage according to claim 9, wherein said at leastone code section comprises code for amplitude modulating saidintermediate signal by controlling a voltage source supplying a poweramplifier.
 16. The machine-readable storage according to claim 9,wherein said expansion is an inverse function of said compression.
 17. Asystem for signal processing, the system comprising: one or morecircuits that, at least: generate a signal that is representative of anamplitude of a pair of baseband signals; expand an amplitude of saidgenerated signal; compress an amplitude of each signal of said pair ofbaseband signals; generate an intermediate signal from said compressedsignals; and amplitude modulate said intermediate signal by saidexpanded signal.
 18. The system according to claim 17, wherein said oneor more circuits square each signal of said pair of baseband signals andcalculate a square root of a sum of said squared signals to generatesaid signal that is representative of an amplitude of said pair ofbaseband signals.
 19. The system according to claim 17, wherein said oneor more circuits generate said intermediate signal by up-converting saidcompressed signals and combining said up-converted signals.
 20. Thesystem according to claim 19, wherein said one or more circuitsup-convert said compressed signals by mixing an in-phase signal of saidcompressed signals with a first local oscillator signal and mixing aquadrature-phase signal of said compressed signals with a second localoscillator signal, wherein said first local oscillator signal and saidsecond local oscillator signal are in phase-quadrature.
 21. The systemaccording to claim 17, wherein said one or more circuits amplitudemodulate said intermediate signal by controlling a gain of a poweramplifier.
 22. The system according to claim 17, wherein said one ormore circuits amplitude modulate said intermediate signal by controllinga current source supplying a power amplifier.
 23. The system accordingto claim 17, wherein said one or more circuits amplitude modulate saidintermediate signal by controlling a voltage source supplying a poweramplifier.
 24. The system according to claim 17, wherein said expansionis an inverse function of said compression.